Present furrow marker units employ a single earth working tool, usually a cutting disc. The single disc cutter includes a concave surface on the disc to cut and throw soil away from the planter or, if the disc is reversed, to cut and pull dirt towards the planter. Either method produces a marker furrow with one clean cut side formed by the convex surface and a more pronounced scattering of earth on the opposite side.
This narrow, uneven type of marker furrow has four disadvantages. First, a planter operator following the furrow by visual means alone has great difficulty in following the true center particularly with wider, modern equipment which places the operator further from the marker furrow. Secondly, if tractor or implement automatic guiding mechanisms are employed, conventional marker furrows do not provide sufficient uniform side slopes and bottom for smooth operation. Third, the present trend toward reduced tillage methods requires a more well defined marker furrow than the single disc cutter affords. Crop remnants associated with such reduced tillage methods obscure shallow, narrow or partially formed furrows. Finally, a single disc marker furrow will not stand up to the spring and summer storms to which most farm lands are subjected.